Which organism is commonly used as an indicator of early ecological succession and can colonize bare rock?

• A. Lichen
• B. Oak
• C. Pine
• D. Moss

Answer: (A)

Lichens are classic pioneers in primary succession. They can colonize bare rock because they don’t need soil to start life; a partnership between a fungus and an algae or cyanobacterium lets them survive on minimal nutrients, tolerate dry, sunny, and harsh conditions, and slowly establish themselves on rock surfaces. As they grow, lichens chemically weather the rock and trap dust and organic material, starting to form a tiny layer of soil. That thin soil then enables other organisms to move in, marking the very first stage of ecological development. While mosses can also appear early, and trees like oaks or pines require more developed soil and better conditions, lichens are the most representative and reliable indicators of initial colonization on bare rock.